This invention relates generally to large tanks for storing and transporting liquids in bulk and more particularly to a sliding gate valve for such a tank to facilitate discharge of the tank contents.
Portable tanks generally have a bottom discharge which is closed by a plug or a short section of piping having a conventional valve at the end of the section. Portable tanks are normally designed to maximize the usable volume within the tank. Accordingly, the less space that is required for discharge connection components such as a plug or valve assembly, the more volume that can be allocated for bulk storage.
Because of the desirability for a compact size in portable tank design, where space is at a premium, a compact tank discharge and valve fitting which allows complete discharge of the tank contents is desirable. In addition, such a discharge should be lockable to prevent accidental discharge of the tank contents.
Specifically in tanks designed for bulk liquid handling and storage, it is often desirable to have a discharge valve that is full ported to minimize restriction to flow through the discharge opening. Accordingly, a design which also breaks the formation of a vortex in the fluid during discharge is preferred. The valve must be capable of positive sealing to prevent leakage in both the open and closed valve positions as well as in an intermediate position. Finally, the discharge valve for a portable tank must be easy to operate.
It is therefore an object of the present invention to provide an compact discharge valve for a portable tank which occupies minimal space below the tank.
It is another object of the present invention to provide a sliding gate valve for a portable tank that is lockable in the closed position by insertion of a bung into the tank discharge opening.
It is still another object of the present invention to provide a sliding gate valve for a portable tank that can tolerate high fluid pressures and has a full ported opening to maximize the discharge flow rate from the tank.
It is still another object of the present invention to provide a gate valve assembly in which the fluid pressure on the gate is at right angles to the direction of movement of fluid discharging from the valve to thereby break the formation of a vortex in the fluid during discharge.
The valve assembly for a liquid containing tank according to the present invention includes a hollow valve body having an outer tubular member which is closed at one end by a disk shaped end portion. This outer member has at least one radial aperture through the member adjacent the closed end. Inside and concentric to the outer tabular member is an inner tubular member having one end attached to the end portion. This inner tubular member also has at least one aperture through the member thus forming a passage through the hollow valve body. Passage of liquid from the tank flows into the valve body through the apertures and out through the center of the inner tubular member.
The opening of the liquid containing tank is bounded by a threaded sleeve extending outward from the wall of the tank. The hollow valve body is positioned concentrically within the sleeve and is held in place by a threaded collar which is threadably engaged with the threaded sleeve. A flange on the threaded collar clamps the valve body in place.
Between the inner and outer tubular members of the hollow valve body is a movable tubular gate member. The tubular gate member can move axially and circumferentially of the body between a closed position fully inserted against the end portion, closing off the passage through the body, and an open position spaced from the end portion so as to open the passage through the body.
The valve assembly according to the present invention provides a full ported opening at the bottom of the tank enabling complete discharge of the tank contents. In addition, the design with a tubular gate member which closes off the passage in a guillotine fashion, means that fluid pressure works generally normal to the opening direction of the gate member. Therefore pressure from the tank contents against the tubular gate member is minimized enhancing the ease with which the valve can be operated.
The valve according to the present invention is fully ported which permits a large volume discharge rate. Such a large flow rate tends to form vortices in the throat of the discharge opening. However, the present invention minimizes the formation of vortices by changing the direction of and splitting the fluid entry into the discharge opening into several circumferential components.
The tubular valve according to the present invention utilizes elastic O-rings between the movable and stationary members to provide a fluid tight seal. In addition, a system of secondary seals using the threaded bung keeps fluid from leaking out when the valve is closed in the event of O-ring leakage.
Further objects, features and advantages of the invention will become evident from a consideration of the following description when taken in conjunction with the accompanying drawing and the appended claims.